High Néel temperature and magnetism modulation in 2D pentagon-based structures XN2 (X = B, Al, Ga) with spin-polarized non-metallic atoms

Abstract

Magnetic semiconductors with spin-polarized non-metallic atoms are usually ignored in applications because of their poor performances in magnetic moments and critical temperatures. Here, magnetic characteristics of 2D pentagon-based XN2 (X = B, Al, Ga) are revealed based on first-principles calculations. It has been proved that XN2 are antiferromagnetic semiconductors with bandgaps of 2.15 eV, 2.42 eV and 2.16 eV respectively. Through analyses of spin density distributions and molecular orbitals, magnetic origin is located at the antibonding orbitals (π*2px and π*2pz) of covalently bonded N atoms. Furthermore, it has also been demonstrated that XN2 have Néel temperatures (TN) of as high as 136 K, 266 K and 477 K through Monte Carlo (MC) simulations of the Ising model. More significantly, the phase transition of magnetic ground state from antiferromagnetic order to ferromagnetic order, continuous distribution of bandgaps from 2.0 eV to 2.5 eV, and enhancement of magnetic moment from 0.3 µB to 1.2 µB can be realized by exerting external fields. Our work proposes a novel spin-polarized phenomenon based on the covalent bond, ameliorating the performances of magnetic semiconductors with spin-polarized p orbit electrons and providing immense application potentials for XN2 in spintronic devices.